The present invention is related to the field of data communications networks.
It is known to use network devices such as routers, switches and bridges to forward data packets within data communications networks. A router is an example of a device operating at the network layer, or layer 3 of the well-known Open Systems Interconnect (OSI) model. Bridges and switches are examples of layer-2 devices.
It is known to define so-called “virtual private networks” or VPNs within larger (often public) networks such as the global Internet. A VPN can be seen as a collection of specialized network devices and/or specialized functions on otherwise standard network devices that co-operate to carry out data communications in a manner that segregates such communications from other data communications carried by the larger network. There are a variety of known VPN technologies, including technologies based on the Internet Protocol (IP), virtual local area network (VLAN) technologies, and virtual private dial-up networks (VPDNs). Routers may offer support for layer-3 VPNs through the use of multiple so-called “virtual routing and forwarding.” tables or VRFs. The VRFs correspond to multiple independent “virtual routers” within a physical router, with each virtual router operating as a node on a corresponding VPN. VLANs generally employ bridging or switching instances located within network devices.